I was invited to participate in the Google foobar challenge in 2018. Google foobar challenge is a set of coding challenges designed to recruit programmers for Google. Though I am not a software developer, I participated anyway and I find the challenge incredibly fun. My solutions are not perfect, but they were mostly original. The exception being level 4b, which was a maximum flow problem. I had to find an algorithm online, but I did implement it on my own.
The Level 5 solution passed the small test cases, but wasn't fast enough for Google's own test cases. I didn't have enough time before further optimization can be added. I will probably try that in the future.
Challenge readme files belong to Google, obviously.